CN111867468B - Physical activity determination system - Google Patents

Abstract

A physical activity determination system (100) for determining the presence or absence of physical activity of a subject (S) on a Bed (BD) is provided with: a plurality of load detectors (11, 12, 13, 14) each for detecting a load of the subject on the bed; a respiratory waveform acquisition unit (32) that obtains a respiratory waveform of the subject based on temporal variations in the load of the subject detected by each of the plurality of load detectors; and a physical activity determination unit (33) that determines whether or not there is physical activity in the subject based on a comparison between a standard deviation of a temporal variation in the load of the subject detected by at least one of the plurality of load detectors and a first threshold. The body motion determination unit compensates the standard deviation used for the comparison by the amplitude of the respiration waveform.

Description

Physical activity determination system

Technical Field

The present invention relates to a physical activity determination system that determines the presence or absence of physical activity of a subject in a bed based on a detection value of a load detector.

Background

In the field of medical care and nursing care, it has been proposed to detect a load of a subject on a bed via a load detector and determine a state of the subject based on the detected load. Specifically, for example, it is proposed to determine the presence or absence of physical activity of the subject based on the detected load.

Patent document 1 discloses a physical activity level determination device that determines a physical activity level of a user in a bed step by step based on a detection value from a load sensor disposed under the legs of the bed. Patent document 2 discloses a sleep determination device and a turn-over detection device that can determine that a person in a bed has physical activity based on the detection results of load sensors disposed under the legs of the bed.

Patent document 1 Japanese patent laid-open No. 2014-195543

Patent document 2, specification of japanese patent No. 5998559.

Disclosure of Invention

The purpose of the present invention is to provide a physical activity determination system capable of more accurately determining whether or not a physical activity has occurred in a subject in a bed based on the detection value of a load detector.

According to a first aspect of the present invention,

provided is a physical activity determination system for determining the presence or absence of physical activity of a subject in a bed, the physical activity determination system being characterized in that,

the disclosed device is provided with:

a plurality of load detectors which are a plurality of load detectors and each of which detects a load of the subject on the bed;

a respiratory waveform acquisition unit that obtains a respiratory waveform of the subject based on temporal variations in the load of the subject detected by each of the plurality of load detectors; and

a physical activity determination unit that determines whether or not there is physical activity of the subject based on a comparison between a standard deviation of a temporal variation in the load of the subject detected by at least one of the plurality of load detectors and a first threshold value,

the body motion determination unit compensates the standard deviation used for the comparison by the amplitude of the respiration waveform.

In the physical activity determination system according to the first aspect, the physical activity determination unit may compensate the standard deviation used for the comparison by using a latest amplitude of the respiration waveform obtained based on a latest peak value of the respiration waveform at a time when the determination of the presence or absence of physical activity of the subject is performed and a peak value immediately before the latest peak value.

In the physical activity determination system according to the first aspect, the physical activity determination unit may compensate the standard deviation used for the comparison by an average value of the latest amplitude of the respiration waveform and at least one amplitude of the respiration waveform in a period before a time when the latest amplitude is obtained.

In the physical activity determination system according to the first aspect, the physical activity determination unit may continue the compensation of the standard deviation using the latest amplitude at the time when the physical activity of the subject is determined to be present, after determining that the physical activity of the subject is present.

In the physical activity determination system according to the first aspect, the compensation is performed by dividing the standard deviation by the amplitude of the respiration waveform.

In the physical activity determination system according to the first aspect, the plurality of load detectors may include a first load detector, a second load detector, a third load detector, and a fourth load detector, and a first standard deviation of temporal fluctuation of the load of the subject detected by the first load detector may be defined as σ₁And a second standard deviation of the temporal variation of the load of the subject detected by the second load detector is represented by σ₂And a third standard deviation of the temporal variation of the load of the subject detected by the third load detector is represented by σ₃And a fourth standard deviation of the temporal variation of the load of the subject detected by the fourth load detector is represented by σ₄The average value is defined as A_AVnThe body motion determination unit may be based on σ₁/A_AVn、σ₂/A_AVn、σ₃/A_AVnAnd sigma₄/A_AVnThe presence or absence of physical activity of the subject is determined by comparing the simple average value of (a) with a first threshold value.

In the physical activity determination system according to the first aspect, the physical activity determination unit may determine a period in which the standard deviation is equal to or less than a predetermined value as a rest period in which the subject breathes only, and may compensate the standard deviation used in the comparison in general by the amplitude of the respiration waveform in the rest period.

The physical activity determination system according to the first aspect may further include: a nonnegativity average value calculation unit that calculates a nonnegativity average value of the detection values of the load detectors; and a threshold setting unit that sets a second threshold used for determining whether or not the subject is physically active, based on the non-negative average calculated during a quiet period in which the subject is breathing only, wherein the physical activity determination unit may be configured to determine whether or not the subject is physically active based on a comparison between the standard deviation and the second threshold, and after it is determined that the subject is not physically active by the determination, determine whether or not the subject is physically active based on a comparison between the standard deviation and the first threshold, and may compensate for the standard deviation used for the comparison with the first threshold, based on the amplitude of the respiratory waveform determined during a period in which the subject is not physically active based on the determination based on the comparison between the standard deviation and the second threshold.

According to a second aspect of the present invention, there is provided a bed system comprising:

a bed; and

a physical activity determination system of a first aspect.

The physical activity determination system of the present invention can determine with higher accuracy whether or not a subject on a bed is experiencing a physical activity based on the detection value of the load detector.

Drawings

Fig. 1 is a block diagram showing a configuration of a physical activity determination system according to an embodiment of the present invention.

Fig. 2 is an explanatory diagram showing the arrangement of the load detector with respect to the bed.

Fig. 3 is a flowchart showing a physical activity determination method using the physical activity determination system.

Fig. 4 is a schematic graph showing the change in the load value detected by the load detector for both the quiet period during which the subject breathes only and the period during which the subject is performing physical activity.

Fig. 5 (a) is an explanatory diagram conceptually showing a case where the center of gravity of the subject vibrates in the body axis direction of the subject in correspondence with the breathing of the subject. Fig. 5 (b) is a graph showing an example of a respiration waveform drawn based on the vibration of the center of gravity of the subject corresponding to the respiration of the subject.

Fig. 6 is an explanatory diagram for explaining an example of a specific method of the physical activity determination by the physical activity determination unit.

Fig. 7 is a block diagram showing a configuration of a biological state monitoring system according to the reference system.

Fig. 8 is a flowchart showing a biological state monitoring method using a reference biological state monitoring system.

Fig. 9 is a block diagram showing a specific configuration of a body motion determination unit included in a biological state monitoring system of the reference system.

Fig. 10 is a flowchart showing a procedure of a physical activity determination process performed by the physical activity determination unit included in the biological state monitoring system of the reference system.

Fig. 11 (a) and 11 (b) are explanatory diagrams for explaining a method of obtaining a non-negative average value for a predetermined period of the detection value of the load detector that fluctuates only in accordance with the breathing of the subject. Fig. 11 (a) is a graph schematically showing a change in the detection value before the non-negativity processing is performed, and fig. 11 (b) is a graph schematically showing a change in the detection value after the non-negativity processing is performed.

Fig. 12 is a graph schematically showing the magnitude (standard deviation) of variation in the detection value of the load detector corresponding to the breathing of the subject and the magnitude (standard deviation) of variation in the detection value of the load detector corresponding to small physical activity of the subject for a subject with a small breathing amplitude, a subject with an average breathing amplitude, and a subject with a large breathing amplitude, respectively.

Fig. 13 is a block diagram showing the overall configuration of the bed system according to the modification.

Detailed Description

The physical activity determination system 100 (fig. 1) according to the embodiment of the present invention will be described by taking, as an example, a case where it is used together with a bed BD (fig. 2) to determine whether or not there is physical activity of a subject S on the bed BD.

As shown in fig. 1, the physical activity determination system 100 of the present embodiment mainly includes a load detection unit 1, a control unit 3, and a storage unit 4. The load detection unit 1 and the control unit 3 are connected via an a/D conversion unit 2. The control unit 3 is also connected to a display unit 5, a notification unit 6, and an input unit 7.

The load detection unit 1 includes 4 load detectors 11, 12, 13, and 14. The load detectors 11, 12, 13, and 14 are load detectors that detect loads using beam-shaped load sensors, for example. Such load detectors are described in, for example, japanese patent No. 4829020 and japanese patent No. 4002905. The load detectors 11, 12, 13, and 14 are connected to the a/D conversion unit 2 by wires or wirelessly.

As shown in FIG. 2, the 4 load detectors 11 to 14 of the load detector 1 are respectively arranged at the legs BL at the four corners of the bed BD for the subject S₁、BL₂、BL₃、BL₄A caster C mounted on the lower end part of the base₁、C₂、C₃、C₄The following is a description.

The a/D converter 2 includes an a/D converter that converts an analog signal from the load detector 1 into a digital signal, and is connected to the load detector 1 and the controller 3 by wires or wirelessly.

The control unit 3 is a dedicated or general-purpose computer, and has a standard deviation calculation unit 31, a respiratory waveform drawing unit (respiratory waveform calculation unit, respiratory waveform acquisition unit) 32, and a physical activity determination unit 33 built therein.

The storage unit 4 is a storage device that stores data used in the physical activity determination system 100, and a hard disk (magnetic disk) can be used, for example.

The display unit 5 is a monitor such as a liquid crystal monitor that displays information output from the control unit 3 to the user of the physical activity determination system 100.

The notification unit 6 includes a device, such as a speaker, for audibly notifying a predetermined notification based on information from the control unit 3.

The input unit 7 is an interface for performing predetermined input to the control unit 3, and may be a key or a mouse.

The operation of determining the presence or absence of physical activity of a subject in a bed using such a physical activity determination system 100 will be described.

The determination of the presence or absence of physical activity of a subject using the physical activity determination system 100 includes, as shown in the flowchart of fig. 3: a load detection step S11 of detecting the load of the subject S, a standard deviation calculation step S12 of calculating a standard deviation indicating the degree of fluctuation of the detected load, a respiratory waveform drawing step S13 of drawing the respiratory waveform of the subject based on the detected load, a physical activity determination step S14 of determining the physical activity of the subject using the standard deviation found in the standard deviation calculation step S12 and the amplitude of the respiratory waveform drawn in the respiratory waveform drawing step S13, and a display step S15 of displaying the result of the physical activity determination.

[ load detection Process ]

In the load detection step S11, the load of the subject S on the bed BD is detected by the load detectors 11, 12, 13, and 14. The load of the subject S on the bed BD is dispersedly applied to the legs BL arranged at the four corners of the bed BD₁～BL₄The load detectors 11 to 14 below detect the load in a distributed manner.

The load detectors 11 to 14 detect loads (load changes) and output analog signals to the a/D converter 2. The a/D converter 2 converts an analog signal into a digital signal with a sampling period of, for example, 5 milliseconds, and outputs the digital signal (hereinafter referred to as a "load signal") to the controller 3. Hereinafter, the load signals obtained by digitally converting the analog signals output from the load detectors 11, 12, 13, and 14 in the a/D converter 2 will be referred to as load signals s₁、s₂、s₃、s₄。

[ procedure for calculating Standard deviation ]

In the standard deviation calculating step S12, the standard deviation calculating unit 31 calculates the standard deviation for each load signal S₁、s₂、s₃、s₄The standard deviation (moving standard deviation) σ of the sample values included in the predetermined sampling period (for example, 5 seconds) is calculated₁、σ₂、σ₃、σ₄. The calculation can always be done.

The standard deviation shows the magnitude of the difference in the sampled values, so that the subject S is quiet on the bed BD, the load signal S, as shown in FIG. 4₁～s₄Period P with a small amount of fluctuation₁Middle standard deviation sigma₁～σ₄And also becomes smaller. On the other hand, when the subject S moves (the subject S generates physical movement), the load signal S₁～s₄Period p during which the amount of fluctuation of (2) is large₂Middle standard deviation sigma₁～σ₄And also becomes larger.

Thus, during the generation of physical activity by the subject S, the standard deviation σ₁～σ₄The value of (d) is larger than the period during which the subject S is not physically moving.

In the present specification and the present invention, "physical activity" refers to movement of the head, the body (trunk), and the four limbs of a subject. Movement of organs, blood vessels, and the like accompanying respiration, heartbeat, and the like is not involved in physical activity. As an example, the physical activities can be classified into a large physical activity accompanying movement of the body (trunk) of the subject S and a small physical activity accompanying only movement of the limbs and the head of the subject. Examples of the large physical activity include turning over, getting up, and the like, and examples of the small physical activity include movement of hands, feet, and heads during sleep. When the subject has heartbeat, respiration, or physical activity, the load signals s from the load detectors 11 to 14 are accordingly generated₁～s₄And (4) changing. The amount of the fluctuation is in accordance with the amount of the fluctuation corresponding to the heartbeat of the subject S, the amount of the fluctuation corresponding to the respiration of the subject S, the amount of the fluctuation corresponding to the small physical activity of the subject S, and the amount of the fluctuation corresponding to the large physical activity of the subject SThe order of (a) becomes larger.

In the physical activity determination of the subject described in the present specification and the present invention, the load signal s₁～s₄Is negligibly small in the amount of fluctuation corresponding to the heartbeat of the subject S. Therefore, in the present specification and the present invention, the phrase "the subject breathes only", the load value and the load signal "fluctuate only in accordance with breathing" refers to a case where the subject does not perform the physical activity, the load value and the load signal do not show fluctuations in accordance with the physical activity, and does not refer to a case where the subject does not generate the heartbeat, or a case where the load value and the load signal do not include fluctuations in accordance with the heartbeat.

[ respiratory waveform drawing step ]

In the respiratory waveform drawing step S13, the respiratory waveform drawing unit (respiratory waveform calculation unit, respiratory waveform acquisition unit) 32 performs a respiratory waveform drawing operation based on the load signal S₁～s₄A respiration waveform of the subject S is depicted.

Human breathing is performed by moving the ribs and diaphragm, causing the lungs to expand and contract. Here, during inspiration, i.e., when the lungs are inflated, the diaphragm descends downward, and the internal organs also move downward. On the other hand, during expiration, i.e., during lung contraction, the diaphragm rises upward, and the internal organs also move upward. As described in the specification of japanese patent No. 6105703 issued to the applicant of the present application, the center of gravity G slightly moves as the internal organs move, and the moving direction thereof is substantially along the extending direction of the spine (body axis direction).

In the present invention and the present specification, "respiration waveform" means a waveform in which the vibration of the center of gravity of a subject that vibrates in the body axis direction of the subject in accordance with the respiration of the subject is developed on the time axis. The 1 cycle of the respiratory waveform corresponds to 1 breath (expiration and inspiration) of the subject. The amplitude of the respiration waveform is affected by the physical constitution of the subject, the depth of respiration. Specifically, for example, the amplitude is increased when the subject is a large skeleton and the subject breathes deeply, and the amplitude is decreased when the subject is a small skeleton and the subject breathes shallowly.

The respiratory waveform drawing unit 32 draws a respiratory waveform as follows.

The respiratory waveform drawing unit 32 first uses the load signal s from the load detection unit 1₁～s₄The position of the center of gravity G of the subject S is calculated for each sampling time. As shown in fig. 5 (a), the center of gravity G of the subject S vibrates in the direction of the body axis SA of the subject S in correspondence with the breathing of the subject S.

Next, the respiratory waveform drawing unit 32 draws the respiratory waveform BW by plotting the position of the center of gravity G at each time on the vertical axis, with the direction of the body axis SA taken as the vertical axis and the time axis taken as the horizontal axis, and the distance between the position of the body axis SA and the vibration center of the respiratory vibration corresponding to the center of gravity G on the vertical axis ((b) of fig. 5).

The respiratory waveform drawing unit 32 does not necessarily have to actually draw the respiratory waveform, and may simply obtain data representing the respiratory waveform.

[ procedure for determining physical Activity ]

In the physical activity determination step S14, the physical activity determination section 33 uses the standard deviation σ calculated in the standard deviation calculation step S12₁～σ₄And the amplitude of the respiratory waveform BW drawn in the respiratory waveform drawing step S13, to determine whether or not the subject S is physically active.

The determination is specifically performed as follows, for example.

The body movement determination unit 33 first detects the peak value of the respiratory waveform BW drawn in the respiratory waveform drawing step S13, and detects the latest peak value p_nSame previous peak p_n-1Minimum value of the period in between and the latest peak value p_nThe difference between them is the latest amplitude A of the respiration waveform BW_n(fig. 5 (b)). Then, the amplitude A is obtained_nAt an amplitude A_nThe previously calculated amplitude A_n-1、A_n-2Simple average of_AVn. At an average amplitude A_AVnAmplitude a used in the calculation of (1)_nThe number of (a) is arbitrary, and can be set to a number that can be obtained in a sampling period of about 5 seconds as an example.

In addition, to confirm the amplitude A_n、A_n-1、A_n-2And average amplitude A_AVnThe respiratory waveform BW related to the calculation (b) may be a respiratory waveform obtained during a quiet period (a period in which the subject does not generate physical activity but only breathes) (that is, in order to confirm that an error due to the movement of the center of gravity corresponding to the physical activity is not included), and the standard deviation σ may be set₁～σ₄Simple mean value of (a)_AVOr standard deviation σ₁～σ₄Is compared with a threshold value sigma₀A comparison is made. Threshold value sigma₀Is a simple mean value sigma_AVOr standard deviation σ₁～σ₄A smaller value that is less than the value can reliably determine the degree to which the subject S has not generated physical activity (conversely, there may be even a simple average value σ_AVOr standard deviation σ₁～σ₄Is equal to or higher than this value, and the subject S does not have physical activity).

Next, the body-movement determining unit 33 obtains the normalized standard deviation σ s by the following (equation 1)₁～σs₄。

[ number 1]

(equation 1)

σs_m＝σ_m/A_AVn (m＝1、2、3、4)

Then, the calculated normalized standard deviation σ s is calculated₁～σs₄Simple mean value of (a s)_AVIs found based on a simple mean value σ s_AVWith a predetermined threshold value σ s_THTo determine whether the subject S is producing physical activity. Specifically, for example, if the simple average value σ s_AVIs a predetermined threshold value σ s_THThe above results indicate that the subject S is physically moving, and the simple average value σ S_AVLess than a predetermined threshold value σ s_THIt is determined that the subject S does not produce physical activity.

While it is determined that the subject S is not physically moving, the physical activity determination unit 33 targets the respiratory waveform BW on the basis of the respiratory waveform BW acquired by the respiratory waveform drawing unit 32Every 1 cycle, calculate the latest amplitude A_n. Then, the latest amplitude A calculated by the use is used_nValue of (A) newly calculated average amplitude A_AVnAnd the standard deviation σ calculated for each sampling instant (for example, each 5 milliseconds)₁～σ₄The normalized standard deviation σ s is calculated sequentially by (equation 1)₁～σs₄Calculating a simple mean value σ s_AV。

The presence or absence of physical activity of the subject S is determined by calculating the simple average values σ S of the above-mentioned values in sequence_AVIn turn with a predetermined threshold value σ s_THAnd performing comparison to finish.

As a result of the determination, after determining that the subject S has suffered physical activity, the physical activity determination unit 33 stops the average amplitude a_AVnContinues to use the average amplitude A calculated at that time_AVnSimple mean value of (a s)_AVAnd (4) calculating. And based on the calculated simple mean value σ s_AVWith a predetermined threshold value σ s_THThe determination of the presence or absence of physical activity of the subject S is continued. This is because, while the subject S is physically moving, the amplitude and the cycle of the respiratory waveform BW greatly vary due to the influence of the physical movement, and it is difficult to calculate the new amplitude a without an error_nAnd average amplitude A_AVn。

Next, when determining that the subject S has no physical activity again, the physical activity determination unit 33 calculates the latest amplitude a based on the respiratory waveform BW acquired by the respiratory waveform drawing unit 32_nAnd using it to recalculate the average amplitude A_AVn. Then, the latest average amplitude A is used_AVnSimple mean value of (a s)_AVBased on the calculated simple mean value σ s_AVWith a predetermined threshold value σ s_THThe determination of the presence or absence of physical activity of the subject S is continued.

A specific example of this step will be described with reference to fig. 6.

As shown in fig. 6, at time t₁The peak value P of the respiration waveform BW is obtained₁Latest amplitude A₁In the case of (3), the physical activity determination unit 33 targets at time t₁The following period, amplitude A is used₁With the amplitude A obtained before it₀、A_－1… (none shown) which is the average amplitude A which is a simple average value_AV1Sequentially calculating normalized standard deviation σ s₁～σs₄And simple mean value σ s_AV(referred to as σ s herein)_AV(A_AV1) And based on a simple mean σ s)_AV(A_AV1) And a threshold value σ s_THThe presence or absence of physical activity of the subject S is determined by the comparison of (1).

Next, at time t₂The peak value p of the respiration waveform BW is obtained₂Latest amplitude A₂In the case of (3), the physical activity determination unit 33 targets at time t₂The following period uses the use amplitude A₂Calculated average amplitude A_AV2Sequentially calculating normalized standard deviation σ s₁～σs₄And simple mean value σ s_AV(referred to as σ s herein)_AV(A_AV2) And based on a simple mean σ s)_AV(A_AV2) And a threshold value σ s_THThe presence or absence of physical activity of the subject S is determined by the comparison of (1).

At time t₂₁When the subject S has moved, the body-movement determining unit 33 determines the body movement based on the simple average σ S_AV(A_AV2) Becomes the threshold value σ s_THIn the above, it is determined that the subject S has generated physical activity. And thereafter for the simple mean σ s_AV(A_AV2) Is the threshold value σ s_THDuring the above period, the simple average value σ s is continuously used_AV(A_AV2) The physical activity of (1).

At time t₂₂When the physical activity of the subject S is completed, the physical activity determination unit 33 determines the physical activity based on the simple average σ S_AV(A_AV2) Less than threshold σ s_THIt is determined that the subject S does not generate physical activity. Thereafter, until the latest amplitude a of the respiration waveform BW is obtained again_nAnd calculating the latest average amplitude A_AVnSo far, the use of the simple average value σ s is continued_AV(A_AV2) The physical activity of (1).

The body motion determination unit 33 uses the amplitude a of the respiration waveform_n(average amplitude A)_AVn) To make the standard deviation sigma₁～σ₄The normalization of the value of (a) is based on the following reason.

As mentioned above, the standard deviation σ₁～σ₄Generally, the value of (b) becomes large during the period in which the subject S generates physical activity. Therefore, it can be conceived to reduce the standard deviation σ₁～σ₄Is compared with a predetermined threshold value to determine whether or not the subject S is physically active.

However, according to the knowledge of the inventors of the present invention, for the standard deviation σ₁～σ₄In the case of a large-sized subject, the amount of movement of the organ corresponding to respiration is also large, and therefore, the value of (2) may be relatively large even during a period in which only respiration is performed without physical activity. In addition, when the physical size of the subject is large, for example, when the subject has taken a deep breath, the value may become relatively large. If the standard deviation sigma is passed₁～σ₄If the physical activity determination is performed by comparing the value of (a) with a predetermined threshold value, in such a case, even if the subject does not generate the physical activity, it is possible to make an erroneous determination that the subject has generated the physical activity.

On the other hand, focusing on the respiration waveform, the amplitude of the respiration waveform is affected by the physique of the subject and the depth of respiration as described above, and becomes larger when the subject is a large skeleton and the subject has made deep respiration, and becomes smaller when the subject is a small skeleton and the subject has made shallow respiration.

I.e. by dividing the standard deviation σ₁～σ₄Is divided by the mean amplitude a of the respiration waveform BW_AVnNormalization is performed to reduce (compensate, correct) the physical constitution of the subject S and the depth of respiration versus the standard deviation σ₁～σ₄The influence of (c) value. Then, by using the normalized standard deviation σ s obtained by such normalization₁～σs₄The physical activity determination of (2) can improve the accuracy of the physical activity determination.

[ display Process ]

In the display step S15, the controller 3 displays the determination result of the physical activity determination step S14 on the display 5. In the display step S15, the report using the report unit 6 may be performed in addition to or instead of the display using the display unit 5. In this case, for example, when the subject S generates a physical activity, a report sound is generated to report the generation of the physical activity to a nurse, a caregiver, or the like, which is a user of the physical activity determination system 100.

The following summarizes the effects of the physical activity determination system 100 of the present embodiment.

The physical activity determination system 100 of the present embodiment uses the standard deviation σ₁～σ₄By the mean amplitude A of the respiration waveform BW_AVnNormalized and compensated (corrected) normalized standard deviation σ s₁～σs₄Simple mean value of (a s)_AVTo make a physical activity determination. Therefore, the variation of the depth of breathing of the subject S, the characteristic pair standard deviation σ of the body₁～σ₄The influence exerted by the value of (2) and the physical activity judgment is reduced, and the judgment precision is high.

The physical activity determination system 100 of the present embodiment calculates the average amplitude a of the respiratory waveform BW based on the respiration of the subject S during a period immediately before the time when the physical activity determination of the subject S is performed_AVnAnd using it to determine the standard deviation sigma₁～σ₄Is normalized. Thus, the standard deviation σ is₁～σ₄Since the normalization of the value of (a) is performed with high accuracy so as to reflect the actual respiratory state of the subject S, the accuracy of the physical activity determination is also high. In addition, the average amplitude A is used as the basis_AVnEven at the amplitude A of the respiration waveform BW_nEven when an abnormal value is generated for some reason, the influence of the abnormal value on the determination is reduced.

The body movement determination system 100 of the present embodiment uses the legs BL disposed on the bed BD₁～BL₄The load detectors 11 to 14 below determine whether the subject S has physical activity. Therefore, it is not necessary to attach a measuring device to the body of the subject S, and discomfort are not given to the subject S.

[ modified examples ]

The following modification can be adopted in the physical activity determination system 100 according to the above embodiment.

In the physical activity determination system 100 of the above embodiment, the standard deviation σ is calculated₁～σ₄Divided by the mean amplitude A of the respiratory waveform BW_AVnTo make the standard deviation sigma₁～σ₄To reduce (compensate, correct) the physique of the subject S, the depth of breathing, and the standard deviation σ₁～σ₄The method of using the compensation (correction) of the amplitude of the respiration waveform BW is not limited to this. Specifically, for example, the latest amplitude a of the respiration waveform BW may be divided by the latest amplitude a_nTo make the standard deviation sigma₁～σ₄Is normalized.

In addition, the standard deviation σ may be compensated using the amplitude of the respiration waveform BW instead₁～σ₄Then, the compensated value is compared with a threshold value, the threshold value is compensated by using the amplitude of the respiration waveform BW, and the standard deviation σ is calculated₁～σ₄And comparing with the compensated threshold value. Specifically, for example, in the above embodiment, the standard deviation σ may be substituted₁～σ₄Divided by the mean amplitude A_AVnBy multiplying a by a predetermined threshold value_AVnTo perform desired compensation (correction). Thus, the two are substantially equivalent, and one of the standard deviation and the threshold value used for the comparison can be compensated (corrected) by appropriately selecting the amplitude of the respiration waveform. In the present specification and the present invention, the phrase "compensating the standard deviation by the amplitude of the respiration waveform" also includes compensating the threshold value by the amplitude of the respiration waveform.

In the physical activity determination system 100 of the above embodiment, the standard deviation σ s is normalized₁～σs₄Simple mean value of (a)s_AVAnd a threshold value σ s_THThe physical activity determination is performed by comparison, but it is also possible to normalize the standard deviation σ s₁～σs₄With a threshold value, normalizing the standard deviation σ s₁～σs₄A comparison of at least two or more simple mean values with a threshold value, normalized standard deviation σ s₁～σs₄The physical activity determination is performed by comparing the total value of at least two of the above-mentioned values with a threshold value.

In addition, in the physical activity determination system 100 according to the above embodiment, a variance (dispersion) which is a square of the standard deviation may be used instead of the standard deviation. When the variance is normalized by the amplitude of the respiration waveform, the variance may be divided by the square of the amplitude of the respiration waveform. Thus, in the present specification and invention, standard deviations also encompass variances.

The physical activity determination unit 33 may have hysteresis in the threshold used for the physical activity determination. Specifically, for example, a first threshold value and a second threshold value larger than the first threshold value are set in advance, and in a situation where it is determined that the subject S is not physically moving, the simple average value σ S is obtained_AVUntil the value becomes equal to or higher than the second threshold value, it is not determined that the subject S has suffered from physical activity. On the other hand, in a situation where it is determined that the subject S is physically moving, the simple average value σ S is used_AVThe subject S is not judged to have generated physical activity even if the second threshold value becomes insufficient, but the simple average value σ S is set to_AVWhen the time becomes less than the first threshold, it is determined that the subject S has not generated physical activity.

< reference means >

The physical activity determination system of the reference system and the biological state monitoring system 200 (fig. 7) including the physical activity determination system will be described by taking as an example a case where it is used together with a bed BD (fig. 2) to determine whether or not there is physical activity of a subject S on the bed BD and estimate the number of breaths.

In the following description, the center of a rectangular bed BD (fig. 2) is defined as a center O, an axis passing through the center O and extending along a short side (width direction) of the bed BD is defined as an X-axis of the bed BD, and an axis passing through the center O and extending along a long side (longitudinal direction, vertical direction) of the bed BD is defined as a Y-axis of the bed BD. In a plan view of the bed BD, the right side of the center O of the bed BD is defined as the positive side of the X axis, the left side is defined as the negative side of the X axis, the upper side of the center O of the bed BD is defined as the positive side of the Y axis, and the lower side is defined as the negative side of the Y axis. When the subject S is lying on the bed BD, the subject S generally lies along the Y axis, with the head placed on the positive side and the foot placed on the negative side in the Y axis direction.

As shown in fig. 7, the biological state monitoring system 200 of the present reference embodiment is the same as the physical activity determination system 100 of the above-described embodiment except that a physical activity determination unit 34 and a respiration rate calculation unit 35 are built in the control unit 3 instead of the standard deviation calculation unit 31, the respiration waveform drawing unit 32, and the physical activity determination unit 33.

In the biological state monitoring system 200 having the above-described configuration, the portion other than the respiration rate calculation unit 35 of the control unit 3 corresponds to the physical activity determination system of the present reference method.

The operation of monitoring the biological state (presence or absence of physical activity, number of breaths) of the subject on the bed using such a biological state monitoring system 200 will be described.

As shown in the flowchart of fig. 8, the monitoring of the biological state of a subject using the biological state monitoring system 200 includes: a load detection step S21 of detecting a load of a subject, a physical activity determination step S22 of determining the presence or absence of physical activity of the subject based on the detected load, a respiration rate calculation step S23 of calculating the respiration rate of the subject with reference to the presence or absence of physical activity of the subject, and a display step S24 of displaying the determination result of the physical activity determination step S22 and/or the calculation result of the respiration rate calculation step S23.

[ load detection Process ]

The content of the load detection step S21 is the same as the content of the load detection step S11 performed in the physical activity determination system 100 of the above-described embodiment.

[ procedure for determining physical Activity ]

In the physical activity determination step S22, physical activity determinationSection 34 uses load signal s₁～s₄Determines the presence or absence of physical activity of the subject S.

As shown in fig. 9, the physical activity determination unit 34 includes a dc component removal unit 341, a standard deviation calculation unit 342, a non-negative average value calculation unit 343, a quiet period determination unit 344, a threshold setting unit 345, and a determination unit 346.

As shown in fig. 10, the physical activity determination step S22 includes a dc component removal step S221, a quiet period determination step S222, a threshold value setting step S223, and a determination step S224.

In the physical activity determination step S22, the physical activity determination unit 34 first performs the operation of removing the dc component from each load signal S using the dc component removal unit 341₁～s₄A dc component removing step S221 of removing the dc component. The dc component is removed specifically, for example, by applying a voltage to each load signal s₁～s₄The moving average value of a predetermined period (for example, 15 seconds) is obtained, and the obtained moving average value is derived from the load signal s₁～s₄Is removed from each sample value.

From the load signal s, the following₁～s₄The signals obtained by removing the DC component are respectively described as load signals sc₁～sc₄。

The load signal sc obtained in the dc component removal step S221 is used in the subsequent quiet period determination step S222, threshold value setting step S223, and determination step S224₁～sc₄To be executed.

The body movement determination unit 34 always performs the calculation of the standard deviation σ by the standard deviation calculation unit 342 and the calculation of the nonnegativity-based average value μ by the nonnegativity-based average value calculation unit 343 on the premise that the quiet period determination step S222, the threshold value setting step S223, and the determination step S224 are performed.

The standard deviation calculation unit 342 calculates the standard deviation for each load signal sc obtained in the dc component removal step S221₁～sc₄The sample value included in the predetermined sampling period (for example, 5 seconds) is always calculatedStandard deviation of (a)₁～σ₄。

The standard deviation σ calculated in the standard deviation calculation unit 342₁～σ₄The determination of the rest period (a period in which the subject does not generate physical activity but merely breathes) in the rest period determination step S222 and the determination of the presence or absence of physical activity of the subject S in the determination step S224 are used (details will be described later).

The non-negating average value calculation unit 343 is configured to calculate the load signal sc for each load signal sc obtained in the dc component removal step S221₁～sc₄The sampling values W included in the predetermined sampling period (for example, 5 seconds) are always calculated₁₁～W₁₄Non-negative of the mean value mu₁～μ₄。

Method for calculating non-negative mean value for load signal sc output in quiet period₁Calculating a non-negative mean value mu of the sampling period between 5 seconds₁The following description will be given by way of example.

As shown in fig. 11 (a), the load signal sc₁During the quiet period, the vibration is only caused to correspond to the breathing of the subject S (as described above, the vibration component corresponding to the heartbeat is also included, but is small and therefore ignored). The non-negating average value calculation section 343 first performs the calculation on the load signal sc₁To determine the sampling value W contained in the sampling period₁₁Minimum value of (3), i.e. minimum sampled value W_min(negative values). Also, the minimum sample value W to be determined_minFrom each sample value W in the sampling period₁₁The value is subtracted to obtain a non-negative value (fig. 11 (b)).

The nonnegativity average value calculation section 343 calculates each of the sampled values W obtained by nonnegativity₁₁To obtain a non-negative mean value mu₁. The load signal sc is likewise calculated₂～sc₄Non-negative of the mean value mu₂～μ₄。

For nonnegative values of the mean value μ obtained during quiet₁～μ₄In other words, if the amplitude of the load fluctuation corresponding to the respiration of the subject S is large, the load fluctuation is largeThe value becomes large, and becomes small when the amplitude of the load fluctuation corresponding to the breathing of the subject S is small.

The nonnegativity average value μ calculated by the nonnegativity average calculation section 343₁～μ₄Threshold value σ in threshold value setting step S223_thThe setting of (1) is used (details will be described later).

Returning to the flowchart of fig. 10, the body-motion determining unit 34 passes the load signal s₁～s₄(and/or the payload signal sc)₁～sc₄) When it is determined that a new subject S is lying on the bed BD, the quiet period determination unit 344 performs the quiet period determination step S222 to determine that the subject S is in a quiet period (a period in which the subject does not generate physical activity and only breathes). Specifically, the determination is made, for example, by comparing the standard deviation σ calculated by the standard deviation calculator 342₁～σ₄Is less than a prescribed threshold value sigma₀(the threshold σ may be the same as the threshold σ used in the physical activity determination system 100 of the above-described embodiment₀Same) is performed.

As mentioned above, the standard deviation σ₁～σ₄In the load signal sc₁～sc₄Has a small period of time, and is in the load signal sc₁～sc₄The period during which the amount of fluctuation of (2) is large. Therefore, during a quiet period (for example, period P in fig. 4) in which the subject S breathes without physical activity₁) Middle standard deviation sigma₁～σ₄Become smaller values. Therefore, if it is used as the threshold σ₀Set a sufficiently small value at the standard deviation σ₁～σ₄Becomes the threshold value σ₀In this case, it can be determined that the subject S is in the quiet period.

In addition, as described later, since there is an individual difference to which the amount of variation in the load signal corresponding to respiration is reduced during a quiet period, there is a possibility that the standard deviation σ may exist depending on the subject during a quiet period in which only respiration is performed without physical activity₁～σ₄Maintained above a threshold value sigma₀The value of (c). In this case, for example, according to the standard deviation σ₁～σ₄Is maintained at the specific threshold value sigma for a predetermined period (for example, 5 to 10 seconds)₀A slightly larger constant value can be determined that the subject is in a quiet period. Breathing usually occurs at a constant rhythm, so if the standard deviation σ is₁～σ₄Continuously being a somewhat small constant value for a predetermined period, even if the value is somewhat larger than the threshold value σ₀The possibility that the period is a quiet period is high.

When the physical activity determination unit 34 determines in the resting period determination step S222 that the subject S is in a resting period, the threshold setting unit 345 performs the threshold setting step S223.

In the threshold setting step S223, the threshold setting unit 345 estimates the magnitude of the respiratory amplitude of the subject S, and sets the threshold σ used in the determination step S224 based on the estimated magnitude of the respiratory amplitude_th。

The breathing amplitude of the subject S is an amplitude of vibration of the center of gravity G of the subject S corresponding to the breathing of the subject S. That is, the respiratory amplitude and the amplitude a of the respiratory waveform BW calculated by the physical activity determination system 100 of the above embodiment_nAre equal.

The threshold setting unit 345 sets the non-negative average value μ calculated by the quiet period non-negative average value calculating unit 343 determined in the quiet period determining step S222₁～μ₄And deduces the magnitude of the respiratory amplitude of the subject S from the magnitude of the selected value. Nonnegativity average value mu in quiet period₁～μ₄In the case of a larger (smaller) signal, it can be said that the load signal S corresponds to the respiration of the subject S₁～s₄、sc₁～sc₄Is larger (smaller), it is inferred that the amplitude of respiration of the subject S is also larger (smaller).

The threshold setting unit 345 then sets the threshold σ used in the determination step S224 based on the estimated magnitude of the respiratory amplitude of the subject S_th. Specifically, for exampleWhen the size of the inferred respiration amplitude is larger than a predetermined threshold value mu_thIn the case of (2), the threshold value σ is set_thSet to a first threshold value σ_th1When the size of the inferred respiration amplitude is smaller than a predetermined threshold value mu_thIn the case of (2), the threshold value σ is set_thSet to the second threshold value σ_th2(＜σ_th1). Thus, the threshold σ is changed in accordance with the magnitude of the respiratory amplitude of the subject S_thThe reason for the size of (2) will be described later.

In addition, the calculated non-negative average value μmay be set so as not to estimate the magnitude of the respiratory amplitude₁～μ₄Any one of (selecting non-negative mean value μ s) and a predetermined threshold value μ_thMaking a comparison at μ_sGreater than a threshold value mu_thWill threshold value σ_thSet to a first threshold value σ_th1At μ_sLess than threshold mu_thWill threshold value σ_thSet to the second threshold value σ_th2(＜σ_th1). In this case, the threshold σ based on the magnitude of the respiratory amplitude of the subject S is substantially completed_thSetting of (4).

Thereafter, the body movement determination unit 34 uses the set threshold σ by the determination unit 346_thThe determination step S224 is executed to determine whether or not the subject S has physical activity. The body-motion determination unit 34 continues to use the threshold σ until the subject S leaves the bed BD_thThereafter, only the determination step S224 may be performed without performing the quiet period determination step S222 and the threshold value setting step S223.

Specifically, for example, the load signal sc calculated by the standard deviation calculator 342 is always used to determine whether the subject S is physically active₁～sc₄Standard deviation of (a)₁～σ₄Any of (hereinafter, referred to as "selection standard deviation σ_SE") and the threshold value σ set in the threshold value setting step S223_thA comparison is made.

During the period when the subject S is producing physical activity, the load signal sc₁～sc₄Becomes large in the amount of variation, the standard deviation σ₁～σ₄And selecting the standard deviation sigma_SEAlso increases (as an example, the period p in FIG. 4₂). Therefore, the standard deviation σ will be chosen_SEAnd a set threshold value sigma_th(i.e.,. sigma.)_th1Or σ_th2) Comparing, selecting standard deviation sigma_SEGreater than a threshold value sigma_thWhen the determination result (2) is positive, it is determined that the subject S generates physical activity.

Here, the physical activity determination unit 34 of the present reference method refers to the magnitude of the respiratory amplitude of the subject S, and sets a different threshold value σ for each subject S_thThe reason for this is as follows.

As described above, the load signals s from the load detectors 11 to 14₁～s₄The amount of the fluctuation varies according to the heartbeat, respiration, and physical activity of the subject S, but the amount of the fluctuation varies according to the characteristics (height, weight, body fat rate, muscle mass, and the like) of the body of the subject S, and the like. Further, according to the findings of the present inventors, there is a correlation to some extent between the amount of load fluctuation (the magnitude of the breathing amplitude) corresponding to breathing and the amount of load fluctuation corresponding to physical activity.

Fig. 12 is a graph schematically showing this situation. In fig. 12, white circles indicate an upper limit value (respiration fluctuation upper limit value BL max) of the amount of load fluctuation (indicated by a standard deviation in fig. 12) that can be indicated in correspondence with the respiration of the subject S, and black circles indicate a lower limit value (physical activity fluctuation lower limit value BD min) of the amount of load fluctuation that can be indicated in correspondence with the physical activity (small physical activity) of the subject.

As shown in FIG. 12, the subject S with a small respiratory amplitude_SUpper limit value BL of respiration fluctuation_maxAnd lower limit of physical activity fluctuation BD_minUpper limit value BL of respiratory variation of subject SM respectively smaller than respiratory amplitude average_maxAnd lower limit of physical activity fluctuation BD_min. On the other hand, the subject S with a large respiratory amplitude_LUpper limit value BL of respiration fluctuation_maxAnd lower limit of physical activity fluctuation BD_minRespectively greater than the respiratory amplitude mean of the subject S_MUpper limit value BL of respiration fluctuation_maxHarmonizing bodyLower limit of body movement BD_min。

Here, according to the findings of the inventors of the present invention, as shown in fig. 12, there is a subject S whose respiration amplitude is large_LUpper limit value BL of respiration fluctuation_maxGreater than the subject S with a smaller breathing amplitude_SLower limit of physical activity fluctuation BD_minThe case (1). Therefore, it is difficult to accurately perform the breathing amplitude of the subject S with a small breathing amplitude using only a single threshold value_SDetermination of physical activity and subject S with large respiratory amplitude_LThe physical activity of (1).

That is, if it is assumed that the subject S having a large respiratory amplitude can be accurately performed_LUsing a comparison subject S_LUpper limit value BL of respiration fluctuation_maxIs larger and larger than the subject S_LLower limit of physical activity fluctuation BD_minSmall threshold value sigma_th1(FIG. 12), the subject S can be accurately performed_LBut with respect to the subject S whose respiration amplitude is small_SIs present in a subject S_SIf a small amount of physical activity occurs, there is a fear that erroneous determination of the physical activity does not occur.

On the contrary, if the subject S with a small breathing amplitude is assumed to be able to accurately perform_SUsing a comparison subject S_SUpper limit value BL of respiration fluctuation_maxIs larger and larger than the subject S_SLower limit of physical activity fluctuation BD_minSmall threshold value sigma_th2(FIG. 12), the subject S can be accurately performed_SBut with respect to the subject S with a large respiration rate_LIs present in a subject S_LWhen only breathing is performed, there is a possibility that erroneous determination of physical activity occurs.

Therefore, in the biological state monitoring system 200 of the present reference system, the threshold value σ corresponding to the subject S is set based on the magnitude of the respiratory amplitude of the subject S_thAnd using a set threshold value sigma_thAnd judging whether the physical activity of the examinee S exists or not. Thus, it is possible to accurately determine how many respiratory amplitudes are different in magnitudeEach subject S had a physical activity.

[ procedure for calculating respiration rate ]

In the respiration rate calculation step S23, the respiration rate calculation unit 35 calculates the respiration rate based on the load signal S₁～s₄Calculates the number of breaths of the subject S.

The calculation of the number of breaths of the subject S by the breath number calculating unit 35 is specifically performed on the load signal S, for example₁～s₄(or the load signal sc)₁～sc₄) At least one of the above is subjected to fourier analysis, and the peak frequency occurring in a frequency band corresponding to respiration (human respiration is about 12 to 20 times in 1 minute, and therefore about 0.2Hz to about 0.33Hz) is determined. The number of breaths of the subject S during this period can be calculated (inferred) from the determined peak frequency.

In addition, the period during which the subject S generates physical activity (as an example, the period P in fig. 4)₂) A period during which the subject S breathes only (for example, the period P in fig. 4)₁) Differently, the load signal s₁～s₄、sc₁～sc₄The vibration is made at a different frequency (or, the vibration is not displayed) from the vibration corresponding to the breathing of the subject S. Therefore, even the load signal s to be obtained during such a period₁～s₄、sc₁～sc₄Also, when applied to fourier analysis, it is difficult to accurately calculate the number of breaths of the subject S.

Therefore, the respiration rate calculation unit 35 of the present reference method stops the calculation of the respiration rate for the period in which the subject S is experiencing physical activity, based on the determination result of the physical activity determination unit 34. The number of breaths in the period may be an estimated value based on the number of breaths in the period before and after the period, or may be an ambiguous value.

[ display Process ]

In the display step S24, the controller 3 displays the determination result in the physical activity determination step S22 and/or the calculation result in the respiration rate calculation step S23 on the display 5. In the display step S24, the report using the report unit 6 may be performed in addition to or instead of the display using the display unit 5. In this case, for example, when the subject S generates a physical activity, a report sound is generated to notify a nurse or a care worker who is a user of the biological state monitoring system 200 of the generation of the physical activity.

The effects of the physical activity determination system of the present reference system and the biological state monitoring system 200 including the same are summarized below.

In the physical activity determination unit 34, the physical activity determination system of the present reference embodiment and the biological state monitoring system 200 including the same set the threshold value σ suitable for each subject S based on the respiratory amplitude of the subject S_thAnd uses it to make a determination as to whether the subject S is producing physical activity. Therefore, the presence or absence of physical activity can be accurately determined for each of the plurality of subjects S having different breathing amplitudes.

In the biological state monitoring system 200 of the present reference embodiment, the respiration rate calculation unit 35 excludes the period in which the calculation of the respiration rate of the subject S is difficult from the calculation target of the respiration rate based on the determination result of the physical activity determination unit 34. Therefore, the reliability of the respiration rate of the subject S calculated by the respiration rate calculating unit 35 is high.

The physical activity determination system of the reference system and the living body state monitoring system 200 including the same use the legs BL disposed on the bed BD₁～BL₄The load detectors 11 to 14 below monitor the biological state of the subject S. Therefore, it is not necessary to attach a measuring device to the body of the subject S, and discomfort are not given to the subject S.

The following modifications can be adopted in the physical activity determination system of the reference system and the biological state monitoring system 200.

In the physical activity determination unit 34 of the reference system, the determination unit 346 may set the threshold σ used in the determination step S224 every time the determination unit determines that the subject S has physical activity in the determination step S224, i.e., may perform the rest period determination step S222 and the threshold setting step S223 again, and may set the threshold σ used in the determination step S224_th。

The magnitude of the breathing amplitude of the subject S substantially depends on the characteristics of the body of the subject S and does not change much during the monitoring period. Therefore, normally, the threshold σ temporarily set in the threshold setting step S23 can be set as long as the subject is not changed_thAnd continues to be used in subsequent monitoring.

However, a patient under near-end care (end-stage medical treatment, end-stage care) often has a change in physical condition to the extent of a change in respiratory amplitude, and such a change in physical condition is often accompanied by physical activity. Therefore, for a patient under end-of-care or the like, the threshold σ is reset for each generation of physical activity_thUsing a threshold value σ corresponding to the physical state at that time_thThus, the accuracy of the physical activity determination can be improved, and the reliability of the calculated respiration rate can be improved.

On the other hand, the nonnegativity-based average value calculation unit 343 of the physical activity determination unit 34 of the above-described reference system temporarily sets the threshold value σ to be the threshold value σ_thWhen the determination step S224 continues to use the memory cell, the threshold σ may be set_thAfter that, the nonnegativity-based mean value μ is stopped₁～μ₄And (4) calculating. Alternatively, the non-negative average value μmay be set only when the quiet period determination unit 344 determines that the subject S is in the quiet period determination step S222₁～μ₄And (4) calculating.

In the above-described reference system, the standard deviation calculation unit 342 of the physical activity determination unit 34 may be used instead of the standard deviation σ₁～σ₄Or calculating the variance σ in addition thereto² ₁～σ² ₄. In this case, the sum-variance σ is also set in the threshold setting step S223² ₁～σ² ₄Corresponding threshold value sigma² _th. In the determination step S224, the variance σ is set² ₁～σ² ₄Any one of them or a sum of any two or more thereof and the threshold value σ² _thAnd comparing the data to judge whether the physical activity of the examinee S exists or not.

In the above referencesIn the embodiment, the body-movement determining section 34 determines the standard deviation σ₁～σ₄Is less than a prescribed threshold value sigma₀The comparison is performed to determine that the subject S is in the quiet period, but the present invention is not limited thereto. The body movement determination unit 34 may set the standard deviation σ₁～σ₄The total value of any two or more of the above is compared with a threshold value, and it is determined that the subject S is in a quiet period.

In the above-described reference mode, the physical activity determination section 34 selects the nonnegativity-based average value μ₁～μ₄And the magnitude of the respiratory amplitude of the subject S is inferred based on the above, but the present invention is not limited to this. The physical activity determination unit 34 may determine the average value μ based on a non-negative value₁～μ₄The magnitude of the respiratory amplitude of the subject S is estimated from the sum of any two or more of the values. For example, if a non-negative mean value μ is used₁～μ₄The sum of (a) and (b) can estimate the magnitude of the respiratory amplitude of the subject S with high accuracy regardless of the position of the subject S on the bed BD.

In the above-described reference mode, the physical activity determination unit 34 sets the threshold value σ_thSet to a first threshold value σ_th1Or a second threshold value sigma smaller than it_th2Any of the above, but not limited thereto. The physical activity determination unit 34 may be configured to determine the average value μ from a non-negative value₁～μ ₄4 the threshold σ is set in more detail in accordance with the magnitude of the respiratory amplitude of the subject S estimated by the estimation unit_thSpecifically, the first threshold σ may be set to be different from each other_th1N threshold value sigma_thn(n is a natural number of 3 or more).

In the above-described reference mode, the physical activity determination unit 34 determines the standard deviation σ₁～σ₄I.e. the selection standard deviation sigma_SEAnd a set threshold value sigma_thThe comparison is performed to determine whether or not the subject S is physically moving, but the present invention is not limited thereto. The body movement determination unit 34 may set the standard deviation σ₁～σ₄A sum of any two or more of the above values and a threshold value σ_thComparing the two to determine the subjectS whether physical activity is produced. In this case, the threshold σ set in the threshold setting step S223 is set to the threshold value σ_thThe standard deviation used in the determination step S224 corresponds to the content.

In the above-described reference aspect, the body-movement determining unit 34 may include a center-of-gravity position calculating unit instead of or in addition to the standard deviation calculating unit 342. The center of gravity position calculating unit uses load signals s from the load detectors 11-14₁～s₄(or the load signal sc)₁～sc₄) Is sampled value W₁₁～W₁₄The position of the center of gravity G of the subject S is calculated (X, Y).

The position (X, Y) of the center of gravity G is calculated by the following calculation. When XY coordinates are set on the bed BD as shown in fig. 2, the coordinates of the load detectors 11, 12, 13, and 14 are (X)₁₁、Y₁₁)、(X₁₂、Y₁₂)、(X₁₃、Y₁₃)、(X₁₄、Y₁₄) The position G (X, Y) of the center of gravity of the load applied to the bed BD is calculated by the following equation.

[ number 2]

(equation 2)

[ number 3]

(equation 3)

The center of gravity position calculation unit calculates the position (X, Y) of the center of gravity G at a predetermined sampling period T based on the above equations 2 and 3, and obtains the temporal variation of the position (X, Y) of the center of gravity G, that is, the center of gravity trajectory GT, and stores the variation in the position in the storage unit 4.

Here, the movement of the center of gravity G of the subject S has the following characteristics.

As described above, the center of gravity G of the subject S vibrates in the direction of the body axis SA of the subject S in correspondence with the breathing of the subject S ((a) of fig. 5). When the subject S has a small physical activity or a large physical activity, the center of gravity G of the subject S moves correspondingly to the small physical activity or the large physical activity. The moving distance of the center of gravity G in the predetermined period increases in the order of a period in which the subject S breathes only, a period in which the subject S performs a small physical activity, and a period in which the subject S performs a large physical activity.

Therefore, the body movement determination unit 34 can determine whether or not the subject S is moving by comparing the moving distance of the center of gravity G for a predetermined period with a predetermined threshold value. Specifically, for example, the moving distance D of the center of gravity G during a predetermined period is larger than a predetermined threshold value D_thIn the case of (3), it can be determined that the subject S has a small physical activity.

In this modification, the body activity determination unit 34 executes the threshold setting step S223 by the threshold setting unit 345, and sets the threshold D corresponding to the magnitude of the breathing amplitude of the subject S_th(e.g., D)_th1And D smaller than it_th2Any of the above).

In the above-described reference system, the respiration rate calculation unit 35 is directed to the load signal s₁～s₄(or the load signal sc)₁～sc₄) At least one of the above is fourier-transformed to calculate the number of breaths of the subject S, but the present invention is not limited thereto.

Specifically, for example, when the body motion determination unit 34 includes a center-of-gravity position calculation unit, the respiratory waveform BW of the subject S can be plotted based on the calculated position of the center of gravity G (fig. 5 (b)). The respiration rate calculation unit 35 can regard the number of oscillations of the respiration waveform BW thus generated as the number of breaths of the subject S.

In this case, when the subject S is physically moving, the center of gravity G of the subject S is largely displaced from the vibration corresponding to the respiration, and the respiration waveform BW is also deviated from the state of vibrating only corresponding to the respiration. Therefore, the physical activity determination unit 34 stops the calculation of the number of breaths when it is determined that the subject S has physical activity.

In the above-described reference system, the control unit 3 may display the generated respiratory waveform BW on the display unit 5.

In the above-described reference method, the body motion determination unit 34 determines that the subject S is in the resting period determination step S222, and estimates the magnitude of the respiratory amplitude of the subject S using the non-negative average value μ in the period. However, the present invention is not limited thereto.

The subject S is rarely moving (moving) all the time on the bed BD, and usually, the subject S does not move (breathes only) and is quiet during most of the time when the subject S is present on the bed BD. Therefore, unless the quiet period is determined, the non-negative average value μ is continuously observed only for a predetermined period (for example, 1 minute or more)₁～μ₄The non-negative mean value mu obtained over time during this period₁～μ₄The smallest value of any one of the above (or the sum of two or more of these) is a value obtained substantially in a quiet period in many cases (in other words, although the quiet period is not clearly determined, the subject is in a quiet state at the time when the smallest value is obtained, and the smallest value is a nonnegative average value in the quiet period in many cases). In this way, the physical activity determination unit 34 may estimate the magnitude of the respiratory amplitude of the subject S based on the smallest value among the non-negative average values obtained over time during the predetermined period.

In this case, if a value smaller than the minimum value of the temporarily obtained non-negative average value is observed, the magnitude of the respiratory amplitude of the subject S may be estimated again based on the value, and/or the threshold σ may be set again if necessary_th。

Or for the load signals s from the load detectors s 11-s 14₁～s₄(or the load signal sc)₁～sc₄) The magnitude of the respiratory amplitude of the subject S can be estimated by performing fourier analysis, extracting only the signal of the respiratory zone, and calculating a non-negative average value based on the extracted signal. According to the method, the body activity antiport can be removed through Fourier analysisCharge signal s₁～s₄(or the load signal sc)₁～sc₄) The influence of (a) can be estimated at an arbitrary timing so as not to determine the rest period.

In the above-described reference method and its modified example, as an example of a method of estimating the magnitude of the respiratory amplitude of the subject S based on the nonnegativity-based average value μ, the magnitude equal to or a predetermined multiple of the nonnegativity-based average value μ, that is, the magnitude of the respiratory amplitude of the subject S can be considered.

In the above-described reference method, the body motion determination unit 34 may calculate the respiratory amplitude of the subject S without using the non-negative average value μ.

Specifically, for example, when the respiration waveform BW is drawn with the center-of-gravity position calculating unit provided, the respiration amplitude of the subject S can be estimated (determined) from the amplitude of the respiration waveform BW. Or based on the load signal s during quiet periods₁～s₄And a load signal sc₁～sc₄Can infer (determine) the amplitude of respiration of the subject S.

The biological state monitoring system 200 of the reference system described above may further include a biological state determination unit that determines another biological state different from the presence or absence of physical activity of the subject S and the number of breaths of the subject S. Such a biological state determination unit performs, for example, determination of whether the subject S is in bed or out of bed, determination of sleep/wake, determination of life and death, and the like, based on the presence or absence of physical activity of the subject S and the number of breaths of the subject S.

Since the biological state monitoring system 200 of the reference system can accurately determine the physical activity of the subject S and estimate the number of breaths of the subject S, the biological state monitoring system 200 according to the modification can accurately determine the presence/absence of the subject S in the bed, the sleep/wake-up, the birth/death, and the like.

The physical activity determination system 100 of the above embodiment does not necessarily need to include all of the load detectors 11 to 14, and may include only one of them. For example, when three load detectors are provided, the center of gravity position G of the subject S on the bed BD can be detected without being arranged on a straight line. The load detectors are not necessarily arranged at the four corners of the bed, and may be arranged at arbitrary positions so as to be able to detect the load and the variation of the subject on the bed. The load detectors 11 to 14 are not limited to load sensors using beam-shaped load sensors, and force sensors, for example, may be used.

In the body movement determination system 100 according to the above-described embodiment, the load detectors 11 to 14 are disposed under the casters C attached to the lower ends of the legs of the bed BD, but the present invention is not limited thereto. The load detectors 11 to 14 may be provided between the 4 legs of the bed BD and the bed plate of the bed BD, or may be provided between the upper leg and the lower leg as long as the 4 legs of the bed BD can be divided into upper and lower parts. Further, the load detectors 11 to 14 may be integrally or detachably attached to the bed BD, and may be configured as a bed system BDs (fig. 13) including the bed BD and the physical activity determination system 100 according to the above-described embodiment.

In the physical activity determination system 100 according to the above embodiment, a signal amplification unit that amplifies the load signal from the load detection unit 1 and a filter unit that removes noise from the load signal may be provided between the load detection unit 1 and the a/D conversion unit 2.

In the physical activity determination system 100 according to the above embodiment, the display unit 5 may be provided with a simple visual display mechanism such as a printer that prints and outputs information indicating whether or not there is physical activity, a lamp that displays whether or not there is physical activity, or the like instead of or in addition to the monitor. The notification unit 6 may include a vibration generation unit that performs notification by vibration instead of or in addition to the speaker.

A physical activity determination system in which the physical activity determination system 100 of the above-described embodiment is used in combination with the physical activity determination system of the above-described reference system can also be constructed. Specifically, the physical activity determination system performs the drawing of the respiratory waveform BW and the average amplitude a after the system start, for example, without reliability_AVnDuring the calculation of (3), the respiratory waveform BW is not taken as the basisIn addition, the physical activity determination is performed by the physical activity determination system of the above-described reference system. Then, the respiratory waveform BW can be reliably plotted and the average amplitude A can be reliably calculated_AVnAt the time of calculation of (a), the physical activity determination by the physical activity determination system 100 of the above embodiment is started. The physical activity determination unit of the physical activity determination system uses the non-negative average value μ immediately after the system is started, for example, in the same manner as the physical activity determination unit 34 of the above-described reference system₁～μ₄Set threshold value sigma_th(second threshold) determination of physical activity of the subject S. Then, when it is determined that the subject S has no physical activity, the average amplitude a of the respiratory waveform BW of the subject S is calculated_AVnThen, the average amplitude A is used_AVnNormalized standard deviation σ s₁～σs₄Simple mean value of (a s)_AVAnd a threshold value σ s_TH(first threshold) of the comparison.

The present invention is not limited to the above-described embodiments as long as the features of the present invention are maintained, and other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Industrial applicability of the invention

According to the physical activity determination system of the present invention, it is possible to reduce the influence of the depth and the physical constitution of the breathing of the subject and determine the presence or absence of physical activity of the subject with high accuracy. Therefore, by using the physical activity determination system of the present invention, high-quality medical treatment and care can be provided based on these highly accurate determinations.

Description of the reference numerals

1 … load detection part; 11. 12, 13, 14 … load detectors; a 2 … A/D conversion section; 3 … control section; 31 … standard deviation calculating part; a 32 … respiratory waveform drawing unit; 33. 34 … body movement determination part; 35 … a respiratory number calculation unit; 4 … storage part; a display portion of 5 …; 6 … report part; 7 … input; 100 … a physical activity determination system; 200 … biological state monitoring system; BD … bed; a BDS … bed system; s … subject.

Claims (9)

1. A physical activity determination system that determines the presence or absence of physical activity of a subject in a bed, the physical activity determination system being characterized in that,

the disclosed device is provided with:

a plurality of load detectors each detecting a load of a subject on the couch;

a respiratory waveform acquisition unit that obtains a respiratory waveform of the subject based on temporal variations in the load of the subject detected by each of the plurality of load detectors; and

a physical activity determination unit that determines the presence or absence of physical activity of the subject based on a comparison between a standard deviation of a temporal variation in the load of the subject detected by at least one of the plurality of load detectors and a first threshold value,

the body activity determiner compensates the standard deviation used in the comparison by the amplitude of the respiration waveform,

the compensation is performed by dividing the standard deviation by the amplitude of the respiration waveform.

2. The physical activity determination system according to claim 1,

the body-activity determining unit compensates the standard deviation used for the comparison by using a latest amplitude of the respiration waveform obtained based on a latest peak value of the respiration waveform at a time when the determination of the presence or absence of body activity of the subject is performed and a peak value immediately before the latest peak value.

3. The physical activity determination system according to claim 2,

the body activity determination unit compensates the standard deviation used for the comparison by averaging the latest amplitude of the respiratory waveform and at least one amplitude of the respiratory waveform in a period before a time when the latest amplitude is obtained.

4. The physical activity determination system according to claim 2,

the body movement determination unit continues compensation of the standard deviation using the latest amplitude at the time when the subject is determined to have the body movement after determining that the subject has the body movement.

5. The physical activity determination system according to claim 3,

the body movement determination unit continues compensation of the standard deviation using the latest amplitude at the time when the subject is determined to have the body movement after determining that the subject has the body movement.

6. The physical activity determination system according to claim 3,

the plurality of load detectors include a first load detector, a second load detector, a third load detector, and a fourth load detector,

a first standard deviation of a temporal variation in the load of the subject detected by the first load detector is represented by σ₁And a second standard deviation of the temporal variation of the load of the subject detected by the second load detector is represented by σ₂A third standard deviation of the temporal variation in the load of the subject detected by the third load detector is represented by σ₃And a fourth standard deviation of the temporal variation in the load of the subject detected by the fourth load detector is represented by σ₄Setting the average value as A_AVnThe determination of the presence or absence of physical activity of the subject based on the comparison between the standard deviation and the first threshold value in the physical activity determination unit is based on σ₁/A_AVn、σ₂/A_AVn、σ₃/A_AVnAnd sigma₄/A_AVnThe presence or absence of physical activity of the subject is determined by comparing the simple average value of (2) with a first threshold value.

7. The physical activity determination system according to any one of claims 1 to 6,

the physical activity determination unit determines a period in which the standard deviation is equal to or less than a predetermined value as a quiet period in which the subject breathes only, and compensates the standard deviation used for the comparison with the amplitude of the respiratory waveform in the quiet period.

8. The physical activity determination system according to any one of claims 1 to 6,

further provided with:

a nonnegativity average value calculation unit that calculates a nonnegativity average value of the detection values of the load detectors; and

a threshold setting unit that sets a second threshold used for determining the presence or absence of physical activity of the subject, based on the non-negative average value calculated during a quiet period in which the subject breathes only,

the body activity determination unit is configured to determine the presence or absence of body activity of the subject based on a comparison between the standard deviation and a second threshold value, determine the presence or absence of body activity of the subject based on a comparison between the standard deviation and a first threshold value after it is determined that the subject is not physically active by the determination, and compensate for the standard deviation used in the comparison with the first threshold value by the amplitude of the respiration waveform during a period in which the subject is determined to be not physically active based on the determination based on the comparison between the standard deviation and the second threshold value.

9. A bed system is characterized by comprising: a bed and the physical activity determination system according to any one of claims 1 to 8.

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